PVC foam compositions

ABSTRACT

The density of rigid foamed articles made by the thermal decomposition of a blowing agent in a vinyl chloride polymer is reduced by the use of an organotin mercaptoalkylcarboxylate, alone, or in combination with an organotin halide or carboxylate which activate the blowing agent. Sulfides made from said organotin mercaptoalkylcarboxylate are also superior activators of the blowing agent.

This is a divisional of application Ser. No. 08/821,185 filed on Mar.19, 1997; now U.S. Pat. No. 5,726,213, which is a C-I-P of Ser. No.08/773,366 filed Dec. 26, 1996, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to the preparation of cellular vinyl chloridepolymers. It relates more particularly to combinations of certainorganotin compounds which are superior activators for blowing agentsemployed in the preparation of cellular vinyl chloride polymers.

One important utility for vinyl chloride resins is in the preparation ofrigid foamed articles. The articles are manufactured by known methodssuch as extrusion of a blend of the resin and additives with a suitableblowing agent and choosing the processing temperature such that it isabove the decomposition temperature of the blowing agent. The bubbles ofgas evolved by the blowing agent are entrapped within the molten resin,thereby forming a cellular structure that are commercially usefularticles such as pipe, decorative molding and structural siding.Usually, the polymer is melted at a temperature between 150° and 200° C.and it is necessary to include a stabilizer in the formulation for thepurpose of eliminating or at least minimizing the heat-induceddiscoloration of the vinyl chloride polymer which would otherwise occurat these temperatures. Also, when the decomposition temperature of theblowing agent is much above the processing temperature, activators areemployed to hasten the decomposition of the blowing agent and/or lowerthe decomposition temperature. The combination of a blowing agent and anactivator increases both the degree and the rate of blowing agentdecomposition. The resultant larger volume of gas generated isdesirable, since it reduces the amount of blowing agent required.

It is a well known fact that a variety of organotin compounds,particularly dibutylin derivatives of mercaptocarboxylic acid esters,will impart useful levels of heat stability to vinyl chloride polymers.German Pat. Nos. 2,133,372 and 2,047,969 disclose the use of organotinmercaptocarboxylic acid esters in foamed polyvinyl chloride. Thesecompounds stabilize well but do not effectively activate blowing agentssuch as azobisformamide. Organotin carboxylates such as dibutyltinmaleate, dibutyltin dilaurate and dibutyltin maleate-half esters aredisclosed in Japanese Pat. No. 6264/67 as being useful in flexible,i.e., plasticized, polymer foams. Although these organotin compoundsactivate azodicarbonamides, they are poor thermal stabilizers for thepolymer. Thus, it can be seen that organotin mercaptocarboxylic acidesters impart good thermal stability but poor blowing agent activation,while organotin carboxylates offer good activation, but poor thermalstability with a resultant lack of proper melt viscosity control.

In addition to dimethyltin-, dibutyltin- anddioctyltin-mercaptocarboxylic acid esters, other compounds that areeffective heat stabilizers for vinyl chloride polymers but poor blowingagent activators are bis(dialkyltin-monomercaptocarboxylic acid ester)sulfides such as bis(dibutyltin-isooctylmercaptoacetate) sulfide,bis(monalkyltin-dimercaptocarboxylic acid ester) sulfides such asbis(monobutyltin-di-isooctylmercaptoacetate) sulfide,(monoalkyltin-dimercaptocarboxylic acid ester)dialkyltin-mercaptocarboxylic acid ester) sulfides, e.g.,(monobutyltin-di-isooctylmercaptoacetate)(dibutyltin-isooctylmercaptoacetate)sulfide, and monoalkyltin tris-mercaptocarboxylic acid esters, e.g.,monobutyltin tris(isooctylmercaptoacetate). organotin carboxylates whichare good blowing agent activators but poor thermal stabilizers, aremonoalkyltin tris(dicarboxylic acid half-esters) such as monobutyltintris(dodecyl maleate), dialkyltin dicarboxylic acid compounds such asdibutyltin azelate, and dialkyltin monocarboxylic acid derivatives,e.g., dibutyltin bis(tall oil fatty acid carboxylate) and dibutyltinbis(benzoate).

The tin mercaptides of the so-called reverse esters are also known to begood stabilizers for vinyl chloride polymers and good activators for theblowing agents. The reverse esters are so called because they are theproducts of the reaction between mercapto-alcohols and carboxylic acidsinstead of between alcohols and mercapto-carboxylic acids. Thepreparation of the esters and the corresponding tin mercaptides, e.g.,dibutyltin bis-(mercaptoethyl laurate), and their use as stabilizers forvinyl chloride polymers are taught in U.S. Pat. No. 2,870,182, which isincorporated herein by reference. Sulfides made by the reaction betweensuch a reverse ester, an organotin chloride, and an alkali metal sulfidein an alkaline aqueous solution and their use as stabilizers for vinylchloride polymers are described in U.S. Pat. No. 4,062,881, which alsois incorporated herein by reference. The sulfides, which may bedescribed as a blend of the reaction products, are also good activatorsfor the blowing agents. The structures of the sulfides, as taught by the'881 patent, are somewhat controversial because of a postulatedequilibrium among them but they are believed to include bis(monoorganotin)-bis(mercaptoalkylcarboxylate)! monosulfides andpolysulfides, bis (diorganotin)-mono(mercaptoalkylcarboxylate)!monosulfides and polysulfides, and products which arise duringequilibrium reactions among said mono- and polysulfides. The chemicaland patent literature contain numerous examples demonstrating thatmembers of different classes of organotin compounds may react with oneanother under certain conditions to yield products containing one ormore tin atoms wherein at least a portion of the tin atoms are bonded todifferent combinations of radicals than they were before being mixedtogether.

Dworkin et al teaches in U.S. Pat. No. 3,953,385 that organotincarboxylates provide only marginal improvement in the activation of ablowing agent when combined with the organotin mercaptocarboxylic acidesters described therein. In contrast to that teaching, we have foundthat a combination of organotin carboxylates and a blend of theorganotin sulfides described above are unexpectedly good activators forthe blowing agents as well as being excellent stabilizers for the vinylchloride polymers. We have also found that organotin chlorides work wellby themselves or in combination with organotin carboxylates asactivators for the blowing agents such as the azobiscarbonamides,5-phenyl tetrazole, and benzene sulfonylhydrazide.

SUMMARY OF THE INVENTION

It is an object of this invention to provide more effective activatorsfor the blowing agents in the preparation of foamed vinyl chloridepolymers.

It is another object of this invention to provide a method for reducingthe density of foamed vinyl chloride polymers while also reducing theamount of blowing agent.

It is a further object of this invention to provide foamed poly(vinylchloride) articles having reduced density and containing reduced amountsof the blowing agent by-products and the blowing agent activator.

These and other objects which will become apparent from the followingdescription of the invention are achieved by a composition consistingessentially of:

a vinyl chloride polymer, a blowing agent, at least one stabilizerselected from the group consisting of:

(A) an organotin mercaptide of a mercaptoalkyl carboxylate having theformula:

    R.sup.1 (4-y)Sn SR.sup.2 OC(═O)R.sup.3 !.sub.y         I

wherein R¹ is an alkyl radical having from 1 to 8 carbon atoms, R² is analkylene radical having from 2 to 18 carbon atoms, R³ is hydrogen, ahydrocarbyl radical, a hydroxyhydrocarbyl radical, or R⁴ C(═O)OR⁵,wherein R⁴ is (CH₂)_(p), phenylene, or --CH═CH--, and R⁵ is ahydrocarbyl radical, p is 0 or an integer from 1 to 8, and y is anynumber from 1 to 3; and

(B) a sulfide of an organotin mercaptide of Formula I; and, optionally,

at least one organotin salt having the formula:

    R'.sub.(4-x) SnX.sub.x                                     III

wherein R' is an alkyl radical having from 1 to 18 carbon atoms, X ishalogen of atomic weight 35 to 127 or a carboxylate ion, and x is from 1to 3.

The sulfide may be made by mixing an alkaline aqueous solution, amercaptoalkyl carboxylate, an alkali metal sulfide or an alkaline earthmetal sulfide, or ammonium sulfide, and an organotin halide having theformula:

    R.sup.6.sub.(4-z) SnHalz                                   II

wherein R⁶ is an alkyl group having from 1 to 18 carbon atoms, Hal is ahalogen having an atomic weight of from 35 to 127, preferably chlorine,and z is any number from 1 to 3.

Alternatively, the sulfide may be made by mixing a monoalkyl- ordialkyltin sulfide with an organotin mercaptide of Formula I, and byother procedures well known in the stabilizer art. The sulfide isbelieved to include bis monoorganotin)-bis(mercaptoalkylcarboxylate)!monosulfides and polysulfides, bis(diorganotin)-mono(mercaptoalkylcarboxylate)!monosulfides andpolysulfides, and products which arise during equilibrium reactionsamong said mono- and polysulfides, including monoalkyltintris(mercaptoalkylcarboxylates), dialkyltinbis(mercaptoalkylcarboxylates, and oligomeric mono- and di-organotinmono- and polysulfides. The sulfide may be described further by theformula: ##STR1## wherein R⁷ is a hydrocarbyl radical; R⁸ is ahydrocarbyl radical or --S--Z-- OC(═O)R⁹ !_(m) ; Z is an alkylene orhydroxyalkylene radical of at least 2 carbon atoms; R⁹ is hydrogen, ahydrocarbyl radical, a hydroxyhydrocarbyl radical, or R¹⁰ C(═O)OR¹¹,wherein R¹⁰ is (CH₂)_(p), phenylene, or --CH═CH--, and R¹¹ is ahydrocarbyl radical; m is an integer from 1 to 3, n is from 1 to 2, p is0 or an integer from 1 to 8, q is from 1 to 10, and the valency of Z ism+1; with the proviso that it includes products arising from anequilibrium among the --SnR⁷, --SnR⁸, and --Sn--S--Z-- OC(═O)R⁹ !_(m),moieties, as recited above.

This invention does not include the use of an organotin(mercaptoalkylcarboxylate) sulfide containing more than 80% by weight ofa (monoorganotin)-bis-(mercaptoalkylcarboxylate) sulfide as a blowingagent activator in a vinyl chloride polymer composition when anorganotin salt of Formula III is not present in the composition.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, a hydrocarbyl radical has from 1 to 20 carbon atoms andincludes alkyl, cycloalkyl, aryl, arylene, alkaryl, aralkyl, aralkenyl,and alkenyl radicals having up to 3 ethylenic double bonds.

The vinyl chloride polymers are made from monomers consisting of vinylchloride alone or a mixture of monomers comprising, preferably, at leastabout 70% by weight based on the total monomer weight of vinyl chloride.They are exemplified by copolymers of vinyl chloride with from about 1to about 30% of a copolymerizable ethylenically unsaturated materialsuch as vinyl acetate, vinyl butyrate, vinyl benzoate, vinylidenechloride, diethyl fumarate, diethyl maleate, other alkyl fumarates andmaleates, vinyl propionate, methyl acrylate, 2-ethylhexyl acrylate,butyl acrylate and other alkyl acrylates, methyl methacrylate, ethylmethacrylate, butyl methacrylate and other alkyl methacrylates, methylalpha-chloroacrylate, styrene, trichloroethylene, vinyl ethers such asvinyl ethyl ether, vinyl chloroethyl ether and vinyl phenyl ether, vinylketones such as vinyl methyl ketone and vinyl phenyl ketone,1-fluoro-2-chloroethylene, acrylonitrile, chloroacrylonitrile,allylidene diacetate and chloroallylidene diacetate. Typical copolymersinclude vinyl chloride-vinyl acetate (96:4 sold commercially as VYNW),vinyl chloride-vinyl acetate (87:13), vinyl chloride-vinylacetate-maleic anhydride ((86:13:1), vinyl chloride-vinylidene chloride(95:5); vinyl chloride-diethyl fumarate (95:5), and vinyl chloride2-ethylhexyl acrylate (80:20).

The vinyl chloride polymers, of course, constitute the major portion ofthe compositions of this invention. Thus, they amount to from about 70%to about 95% by weight of the total weight of the unfoamed compositionsof this invention.

The blowing agent may be any one or a mixture of those commonly used forfoaming PVC pipe, including azobisformamide, 5-phenyl tetrazole, benzenesulfonyl hydrazide, The formula for the azobisformamide is: ##STR2##Azobisformamide is available under the CELOGEN AZRV trademark. Theconcentration of said blowing agent is suitably from about 0.1 and 5.0%but preferably from about 0.2 to about 3% by weight of the totalcomposition prior to the formation of foam.

R' in the organotin salt is preferably an alkyl group having from 1 to 8carbon atoms, more preferably only 1 carbon atom, and when X is halogen,it is preferably chlorine and x is preferably from 2 to 3. When used,the proportion of organotin halide in the unfoamed compositions of thisinvention is from about 5 to about 15% of the weight of the heatstabilizer used in the vinyl chloride polymer composition of thisinvention. When X is a carboxylate ion, it preferably has from 1 to 20carbon atoms and is exemplified by the ions of acetic, propionic,butyric, caprylic, caproic, decanoic, lauric, stearic, oleic, andbenzoic acid. When used, the amount of organotin carboxylate is fromabout 10 to about 80% of the weight of the heat stabilizer used in thevinyl chloride polymer composition of this invention.

The organotin halides may be prepared by methods well known in the artsuch as those disclosed in U.S. Pat. Nos. 3,745,183, 3,857,868, and4,134,878. They are exemplified by methyltin trichloride, dimethyltindichloride, trioctyltin chloride, dibutyltin dibromide, diphenyltindichloride, and dibenzyltin dichloride.

The organotin carboxylates may be prepared by well known conventionalmethods such as by the reaction of an organotinhalide with a carboxylicacid in the presence of a base in water or the reaction of an organotinoxide with the carboxylic acid. They are exemplified by monobutyltintris(dodecylmaleate), dimethyltin azelate, diethyltin dilaurate,monobutyltin tri-tallate, and dimethyltin dibenzoate.

The amount of stabilizer in the unfoamed compositions of this inventionis from about 0.1 to about 10%, preferably from about 0.5 to about 5%,by weight. They may be incorporated into the compositions by admixing inan appropriate mill or mixer or by any of the other well-known methodswhich provide for the uniform distribution of the stabilizers throughoutthe composition.

In the stabilizer (A), R¹ is preferably an alkyl group having from 1 to4 carbon atoms, R² is preferably an alkylene group having from 2 to 8carbon atoms, R³ is preferably an alkyl group having from 1 to 7 carbonatoms or a phenyl group, and y is preferably from 1 to 2. Reverse estersare commonly made from a mixture of monoorgano- and diorganotinchlorides; it is preferred for this invention to use a mixturecontaining from about 70 to about 90, more preferably about 80 weightpercent of the dimethyltin chloride to promote the formation of amixture of the reverse esters having about the same proportion of mono-and diorganotin bis(mercaptoalkylcarboxylates), Reverse esters havingsuch a high concentration of the diorganotin moiety have been found tobe superior activators of the blowing agent without the need for asecond activator such as the organotin halides and organotincarboxylates. The stabilizer comprises, therefore, a mixture ofmercaptides for some of which the value of y in Formula I is 2 and forothers the value of y is 3. It is preferred, that the amount ofmercaptides for which y is 2 is from about 70 to about 90%, morepreferably about 80%, of the total weight of the mixture. As notedabove, the preparation of the mercaptoalkyl carboxylate esters and thecorresponding tin mercaptides, e.g., dibutyltin bis-(mercaptoethyllaurate), is taught in U.S. Pat. No. 2,870,182.

The sulfides may be prepared by any of several well known methods suchas those taught in U.S. Pat. No. 4,062,881.

Thus as starting material there can be used methyltin trichloride,methyltin tribromide, methyltin triiodide, ethyltin trichloride,butyltin trichloride, butyltin tribromide, butyltin triiodide, sec.butyltin trichloride, octyltin trichloride, benzyltin trichloride,dimethyltin dichloride, dimethyltin dibromide dimethyltin diiodide,dipropyltin dichloride, butyl methyl tin dichloride, dibutyltindichloride, dibutyltin dibromide, dioctyltin diiodide, dioctyltindichloride, dibenzyltin dichloride, phenyltin trichloride, p-tolyltintrichloride, diphenyltin dichloride, di-p-tolyltin dichloride,cyclohexyltin trichloride, dicyclohexyltin dichloride, cyclopentyltintrichloride, oleyltin trichloride, dioleyltin dichloride, vinyltintrichloride, diallyltin dichloride, allyltin trichloride, eicosanyltintrichloride.

As the mercaptoalkanol ester there can be employed, for example, estersof mercaptoethanol, 2-thioglycerine, 3-thioglycerine, 3-thiopropanol,2-thiopropanol, 4-thiobutanol, 18-thiooctadecanol, 9-thiononanol,8-thiooctanol, 6-thiohexanol with acids such as formic acid, aceticacid, propionic acid, butyric acid, pivalic acid, valeric acid, caprylicacid, caproic acid, decanoic acid, lauric acid, myristic acid, palmiticacid, 2-ethylhexanoic acid, stearic acid, eicosanic acid, oleic acid,linoleic acid, linolenic acid, crotonic acid, methacrylic acid, acrylicacid, cinnamic acid, benzoic acid, p-toluic acid, o-toluic acid,p-t-butylbenzoic acid, enanthic acid, p-n-butylbenzoic acid, cyclohexanecarboxylic acid, phenylacetic acid, ricinoleic acid, hydrogenatedricinoleic acid, phenylpropionic acid. Of course, mixtures of acids canbe used, e.g., tall oil acids, palmitic acid-stearic acid mixturesranging from 60:40 to 40:60, soybean oil acids, cottonseed oil acids,hydrogenated cottonseed oil acids, peanut oil acids, coconut oil acids,corn oil acids, castor oil acids, hydrogenated castor oil acids, lardacids, etc. Illustrative of half esters of polycarboxylic acids whichcan be esterified with the mercaptoalkanol are monomethyl maleate,monoethyl maleate, monopropyl maleate, monobutyl maleate, monooctylmaleate, mono-2-ethylhexyl maleate, monostearyl maleate, monoethylfumarate, mono methyl oxalate, monoethyl oxalate, monoethyl malonate,monobutyl malonate, monoisopropyl succinate, monomethyl succinate,monomethyl glutarate, monoethyl adipate, monomethyl glutarate, monoethyladipate, monomethyl azelate, monomethyl phthalate, monoethyl phthalate,monoisooctyl phthalate, monoethyl terephthalate.

Illustrate of mercapto esters which can be used in the preparation ofthe tin compound include:

2-mercaptoethyl acetate,

2-mercaptoethyl propionate,

2-mercaptoethyl butyrate,

2-mercaptoethyl valerate,

2-mercaptoethyl pivalate,

2-mercaptoethyl caproate,

2-mercaptoethyl caprylate,

2-mercaptoethyl pelargonate,

2-mercaptoethyl decanoate,

2-mercaptoethyl laurate,

2-mercaptoethyl stearate,

2-mercaptoethyl eicosanate,

2-mercaptoethyl palmitate,

2-mercaptoethyl oleate,

2-mercaptoethyl ricinoleate,

2-mercaptoethyl linoleate,

2-mercaptoethyl linolenate,

2-mercaptoethyl tallate,

2-mercaptoethyl ester of cottonseed oil acid,

2-mercaptoethyl ester of lard acids,

2-mercaptoethyl ester of coconut oil acids,

2-mercaptoethyl ester of soybean oil acids,

2-mercaptoethyl benzoate,

2-mercaptoethyl p-toluate,

2-mercaptoethyl crotonate,

2-mercaptoethyl cinnamate,

2-mercaptoethyl phenyl acetate,

2-mercaptoethyl phenyl propionate,

2-mercaptoethyl methyl maleate,

2-mercaptoethyl ethyl fumarate,

2-mercaptoethyl butyl oxalate,

2-mercaptoethyl methyl oxalate,

2-mercaptoethyl ethyl malonate,

2-mercaptoethyl methyl succinate,

2-mercaptoethyl methyl azelate,

2-mercaptoethyl hexyl azelate,

2-mercaptoethyl methyl phthalate,

3-mercaptopropyl pelargonate,

3-mercaptopropyl enanthate,

3-mercaptopropyl stearate,

3-mercaptopropyl oleate,

3-mercaptopropyl ricinoleate,

3-mercaptopropyl ethyl maleate,

3-mercaptopropyl benzoate,

6-mercaptohexyl acetate,

7-mercaptoheptyl acetate,

7-mercaptoheptyl propionate,

8-mercaptooctyl acetate,

8-mercaptooctyl enanthate,

18-mercaptooctadecyl acetate,

18-mercaptooctadecyl enanthate.

In Formula IV for the sulfide, R⁷ and R⁸ are preferably alkyl groupshaving from 1 to 8 carbon atoms, more preferably 1, Z is preferably analkylene radical having from 2 to 8 carbon atoms, R⁹ is preferably analkyl radical having from 1 to 17 carbon atoms, n is preferably 1, and qis preferably from 1 to 4 and more preferably from 1 to 2.

In addition to the blowing agent activator-heat stabilizer compositionsdescribed in the foregoing specification and appended claims, the vinylchloride polymer compositions of this invention may contain additivesfor the purpose of increasing, resistance to oxidation, flame retardancyand impact resistance of the polymer. Pigments, fillers, dyes,ultraviolet light absorbing agents and the like may also be present.Conventional processing aids such as lubricants and acrylic resins canalso be present.

Acrylic resins are employed in the compositions of this invention asprocessing aids to improve melt elasticity and strength and to preventthe collapse of the cellular structure during processing. The amount ofthe acrylic resin is from about 2 to about 15 parts per hundred parts ofthe vinyl chloride polymer. The molecular weight of the resin may be inthe range of from 300,000 to 1,500,000 but those having the highermolecular weights are preferred; resins having a molecular weight of1,000,000 and higher are particularly preferred. Examples of the acrylicprocessing aids include those sold by Rohm & Haas under the trademarkACRYLOID and product numbers K-175, and K-400.

Among the antioxidants suitable for use in the present polymercompositions are phenols, particularly those wherein the positionsadjacent to the carbon atom bearing the hydroxyl radical contain alkylradicals as substituents. Phenols wherein this alkyl radical issterically bulky, e.g. a tertiary butyl radical, are preferred.

A small amount, usually not more than 0.1%, of a metal release agent,such as an oxidized polyethylene, also can be included.

The effect of the blowing agent activator is independent of whether itis added to the vinyl chloride polymer as an aqueous solution, as partof a stabilizer package, or as part of a lubricant package. A variety ofconventional molding and extruding techniques may be used to form therigid, cellular vinyl chloride polymers of this invention into pipe orany desired profile or a sheet.

The following examples illustrate this invention more specifically.Unless otherwise indicated, all parts and percentages in these examplesand throughout this specification are by weight. ABF is an abbreviationof azobisformamide.

EXAMPLE 1

PVC pipe formulations A and B were processed in a Brabender 3/4 inchextruder having a 25/1 length to diameter ratio and a straight flightscrew having a 2/1 compression ratio and a die orifice of 5 mm. Thetemperature profile (°C.) was:

Zone 1 170 Zone 2 180 Zone 3 190 Die 170.

Formulations A and B are the same except for the addition of themonomethyltin trichloride in B as shown in the following table. Theextrusion results are also given in the table.

                  TABLE 1                                                         ______________________________________                                        FORMULATION    A            B                                                 ______________________________________                                        PVC            100.00  parts    100.00                                                                              parts                                   CaCO.sub.3     5.00    phr      5.00  phr                                     TiO.sub.2      1.00    "        1.00  "                                       Ca stearate    0.75    "        0.75  "                                       AC-629*        0.08    "        0.08  "                                       Paraffin wax   1.30    "        1.30  "                                       Azobisformamide                                                                              0.35    "        0.35  "                                       Monomethyltin  0.70    "        0.70  "                                       tris(mercapto-                                                                ethyl tallate)                                                                sulfide                                                                       Monomethyltin  0.00    "        0.05  "                                       trichloride                                                                   ______________________________________                                        *trademark for oxidized polyethylene                                          Extrusion Results                                                             ______________________________________                                        RPM               50      50                                                  Torque m.gm.      2514    2512                                                Rate gm/hr        3400    3400                                                Melt temperature (°C.)                                                                   205     205                                                 Foam Density gm/cc                                                                              0.74    0.70                                                ______________________________________                                    

EXAMPLES 2-4

PVC pipe formulations 2-4, as well as Control 1 were processed in aBrabender 3/4 inch extruder having a 25/1 length to diameter ratio and astraight flight screw having a 4/1 compression ratio and a die orificeof 5 mm. The temperature profile (°C.) was:

Zone 1 150 Zone 2 160 Zone 3 175 Die 170.

The formulations as well as the extrusion results are as shown in thefollowing table.

                  TABLE 2                                                         ______________________________________                                        FORMULATION**                                                                              Cont 1  2         3     4                                        ______________________________________                                        PVC          100.00  100.00    100.00                                                                              100.00                                   Acrylic resin                                                                 K-400        6.00    6.00      6.00  6.00                                     K-175        0.50    0.50      0.50  0.50                                     CaCO.sub.3   5.00    5.00      5.00  5.00                                     TiO.sub.2    1.00    1.00      1.00  1.00                                     Ca stearate  1.00    1.00      1.00  1.00                                     AC-629       0.1     0.1       0.10  0.10                                     Paraffin wax 0.50    0.50      0.50  0.50                                     Azobisformamide                                                                            0.15    0.15      0.15  0.15                                     Monomethyltin                                                                              1.50    1.50      1.50  1.50                                     tris(inercapto-                                                               ethyl tallate)                                                                sulfide                                                                       Monomethyltin                                                                              0.00    0.40      0.20  0.20                                     trichloride                                                                   ______________________________________                                        **amounts of additive in parts per hundred parts of resin (phr)               Extrusion Results                                                             ______________________________________                                        RPM          45      45        45    45                                       Torque m.gm. 8650    7025      7950  7450                                     Rate gm/min  48.6    45.9      44.8  44.9                                     Melt temp (°C.)                                                                     215     215       212   211                                      Foam Density gm/cc                                                                         0.96    0.85      0.91  0.91                                     ______________________________________                                    

EXAMPLE 5 Cont 2, and Comp Examples 1 and 2

The PVC pipe formulations shown in Table 3 were processed in a Brabender3/4 inch extruder having a 25/1 length to diameter ratio and a straightflight screw having a 4/1 compression ratio and a die orifice of 5 mm.The extrusion results are also given in the table. The temperatureprofile (°C.) was:

Zone 1 150 Zone 2 160 Zone 3 175 Die

                  TABLE 3                                                         ______________________________________                                        FORMULATION**                                                                              Cont 2  CE 1      5     CE 2                                     ______________________________________                                        PVC          100.00  100.00    100.00                                                                              100.00                                   Acrylic resin                                                                 K-400        6.00    6.00      6.00  6.00                                     K-175        0.50    0.50      0.50  0.50                                     CaCO.sub.3   5.00    5.00      5.00  5.00                                     TiO.sub.2    1.00    1.00      1.00  1.00                                     Ca stearate  1.00    1.00      1.00  1.00                                     RHEOLUBE 165 0.50    0.50      0.50  0.50                                     AC-629       0.1     0.1       0.10  0.10                                     Azobisformamide                                                                            0.15    0.15      0.15  0.15                                     Dimethyltin  1.50    --        1.20  --                                       bis(mercapto-                                                                 ethyl tallate)                                                                sulfide                                                                       Dimethyltin  --      1.50      --    1.20                                     bis(2-ethylhexyl                                                              thioglycolate)                                                                Dimethyltin  --      --        0.30  0.30                                     ditallate                                                                     ______________________________________                                        **amounts of additive in parts per hundred parts of resin (phr)               Extrusion Results                                                             ______________________________________                                        RPM          45      45        45    45                                       Torque m.gm. 8700    8150      7450  7900                                     Rate gm/min  44.6    42,8      44.4  43.3                                     Melt temp (°C.)                                                                     209     207       207   206                                      Foam Density gm/cc                                                                         0.56    0.74      0.46  0.63                                     ______________________________________                                    

EXAMPLES 6-8 & CONTROL '2 & COMP EX 3

The PVC pipe formulations shown in Table 4 were processed in a Brabender3/4 inch extruder having a 25/1 length to diameter ratio and a straightflight screw having a 4/1 compression ratio and a die orifice of 5 mm.The extrusion results are also given in the table. The temperatureprofile (°C.) was:

Zone 1 150 Zone 2 160 Zone 3 175 Die

                  TABLE 4                                                         ______________________________________                                        FORMULATION**                                                                            Cont 2   CE 3    6     7     8                                     ______________________________________                                        PVC        100      100     100   100   100                                   Acrylic resin                                                                 K-400      6        6       6     6     6                                     K-175      0.5      0.5     0.5   0.5   0.5                                   CaCO.sub.3 5        5       5     5     5                                     TiO.sub.2  1        1       1     1     1                                     Ca stearate                                                                              1        1       1     1     1                                     AC-629     0.1      0.1     0.1   0.1   0.1                                   Paraffin wax                                                                             0.5      0.5     0.5   0.5   0.5                                   Azobisformamide                                                                          0.35     0.35    0.35  0.35  0.35                                  Dimethyltin                                                                              1.50     --      1.20  0.90  0.60                                  bis(mercapto-                                                                 ethyl tallate                                                                 sulfide                                                                       MARK 1915  --       1.50    --    --    --                                    (Witco)                                                                       Dimethyltin                                                                              --       --      0.30  0.60  0.90                                  ditallate                                                                     ______________________________________                                        **amounts of additive in parts per hundred parts of resin (phr)               Extrusion Results                                                             ______________________________________                                        RPM        45       45      45    45    45                                    Torque m/gm                                                                              8700     6800    7450  6575  7900                                  Rate gm/min                                                                              44.1     46.8    43.4  43.9  43.3                                  Melt temp (°C.)                                                                   209      206     206   204   203                                   Foam Density                                                                             0.56     0.53    0.53  0.52  0.50                                  ______________________________________                                    

EXAMPLES 9-15 & CONTROL '2

The PVC pipe formulations shown in Table 5 were processed in a Brabender3/4 inch extruder having a 25/1 length to diameter ratio and a straightflight screw having a 4/1 compression ratio and a die orifice of 5 mm.The extrusion results are also given in the table. The temperatureprofile (°C.) was:

Zone 1 150 Zone 2 160 Zone 3 175 Die

                                      TABLE 5                                     __________________________________________________________________________    FORMULATION**                                                                          Cont 2                                                                            9   10  11  12  13  14  15                                       __________________________________________________________________________    PVC      100 100 100 100 100 100 100 100                                      Acrylic resin                                                                 K-400    6   6   6   6   6   6   6   6                                        K-175    0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5                                      CaCO.sub.3                                                                             5   5   5   5   5   0.5 0.5 0.5                                      TiO.sub.2                                                                              1   1   1   1   1   1   1   1                                        Ca stearate                                                                            1   1   1   1   1   1   1   1                                        AC-429   0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1                                      Paraffin wax                                                                           0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5                                      Azobisformamide                                                                        0.35                                                                              0.35                                                                              0.35                                                                              0.35                                                                              0.35                                                                              0.35                                                                              0.35                                                                              0.35                                     Dimethyltim                                                                            1.50                                                                              --  --  --  1.20                                                                              --  --  --                                       bis(mercapto-                                                                 ethyltallate) sulfide                                                         Monomethyltin                                                                          --  1.50                                                                              --  --  --  1.20                                                                              --  --                                       tris(mercapto-                                                                ethyltallate) sulfide                                                         Monomethyltin                                                                          --  --  1.50                                                                              --  --  --  1.20                                                                              --                                       bis(mercapto-                                                                 ethyltallate)                                                                 Dimethyltin                                                                            --  --  --  1.50                                                                              --  --  --  1.20                                     (mercapto-                                                                    ethyltallate)                                                                 Dimethyltin                                                                            --  --  --  --  0.30                                                                              0.30                                                                              0.30                                                                              0.30                                     ditallate                                                                     __________________________________________________________________________    **amounts of additive in parts per hundred parts of resin (phr)               Extrusion Results                                                             __________________________________________________________________________    RPM      45  45  45  45  45  45  45  45                                       Torque m.gm.                                                                           8700                                                                              8625                                                                              8825                                                                              8200                                                                              7525                                                                              7900                                                                              7525                                                                              7225                                     Rate gm/min                                                                            44.1                                                                              46.0                                                                              46.9                                                                              46.1                                                                              43.8                                                                              44.3                                                                              44.8                                                                              44.0                                     Melt Temp (°C.)                                                                 209 205 206 204 204 206 205 205                                      Foam Density                                                                           0.56                                                                              0.63                                                                              0.55                                                                              0.51                                                                              0.52                                                                              0.58                                                                              0.55                                                                              0.49                                     gm/cc                                                                         __________________________________________________________________________

The subject matter claimed is:
 1. A rigid, cellular compositionconsisting essentially of a vinyl chloride polymer, at least onestabilizer selected from the group consisting of:(A) an organotinmercaptide of a mercaptoalkyl carboxylate having the formula:

    R.sup.1 (4-y)Sn SR.sup.2 OC(═O)R.sup.3 !.sub.y         I

wherein R¹ is an alkyl radical having from 1 to 8 carbon atoms, R² is analkylene radical having from 2 to 18 carbon atoms, R³ is hydrogen, ahydrocarbyl radical, a hydroxyhydrocarbyl radical, or R⁴ C(═O)OR⁵,wherein R⁴ is (CH₂)_(p), phenylene, or --CH═CH--, and R⁵ is ahydrocarbyl radical, p is 0 or an integer from 1 to 8, and y is anynumber from 1 to 3; and (B) a sulfide of an organotin mercaptide ofFormula I; and, optionally,at least one organotin salt having theformula

    R'.sub.(4-x) SnX.sub.x

wherein R' is an alkyl radical having from 1 to 18 carbon atoms, X is achloride ion or a carboxylate ion, and x is from 1 to 3; with theproviso that when such an organotin salt is not present in thecomposition, the composition is free from an organotinmercaptoalkylcarboxylate sulfide containing more than about 80% byweight of a monoorganotin bis(mercaptoalkylcarboxylate)sulfide.
 2. Thecomposition of claim 1 wherein X is a carboxylate ion has from 1 to 20carbon atoms and x is preferably from 2 to
 3. 3. The composition ofclaim 2 wherein R¹ is an alkyl group having from 1 to 4 carbon atoms, R²is an alkylene group having from 2 to 8 carbon atoms, R³ is an alkylgroup having from 1 to 17 carbon atoms or a phenyl group, and y is from2 to
 3. 4. The composition of claim 1 wherein the sulfide has theformula ##STR3## wherein R⁷ is a hydrocarbyl radical; R⁸ is ahydrocarbyl radical or --S--Z-- OC(═O)R⁹ !_(m) ; Z is an alkylene orhydroxyalkylene radical of at least 2 carbon atoms; R⁹ is hydrogen, ahydrocarbyl radical, a hydroxyhydrocarbyl radical, or R¹⁰ C(═O)OR¹¹,wherein R¹⁰ is (CH₂)_(p), phenylene, or --CH═CH--, and R¹¹ is ahydrocarbyl radical; m is an integer from 1 to 3, n is from 1 to 2, p is0 or an integer from 1 to 8, q is from 1 to 10, and the valency of Z ism+1; with the proviso that it includes products arising from anequilibrium among the --SnR⁷, --SnR⁸, and --Sn--S--Z-- OC(═O)R⁹ !_(m)moieties, including oligomeric organotin sulfides.
 5. The composition ofclaim 1 wherein R⁷ and R⁸ are alkyl groups having from 1 to 8 carbonatoms, Z is an alkylene radical having from 2 to 8 carbon atoms, R⁹ isan alkyl radical having 10 from 1 to 17 carbon atoms, n is 1, and q isfrom 1 to
 4. 6. The composition of claim 4 wherein q is from 1 to
 2. 7.The composition of claim 1 wherein X is a chloride ion.
 8. Thecomposition of claim 2 wherein the organotin carboxylate comprises amixture wherein x is from 2 to
 3. 9. The composition of claim 7 whereinthe organotin chloride comprises a mixture wherein x is from 2 to 3.